1. Field of the Invention
The present invention relates to an optical disk, a recording method for the optical disk and a production apparatus for a master of the optical disk.
2. Description of the Related Art
Pits in a conventional optical disk dedicated for reproduction will be described with reference to FIGS. 1A and 1B. Pits a1, a2 of FIG. 1A are such pits that the width thereof is constant but they are different in length depending on information signal (modulated information signal). To prevent forgery and to improve commercial value, pits b1, b2 of FIG. 1B record a signal for preventing the forgery or characters, graphic or symbol by changing the width or length of the pits a1, a2 of FIG. 1A. The changing of the width and length of the pits can be carried out by changing an exposure amount on an exposure master disk for the optical disk upon recording.
A groove in a conventional recordable (of course reproducible) optical disk will be described with reference to FIGS. 2A and 2B. An optical disk of FIG. 2A comprises a groove G having a predetermined constant width and a land L having a predetermined constant width between the grooves G, thereby information signal (modulated information signal) being recorded on a bottom of the groove G. An optical disk shown in FIG. 2B indicates a case in which the width of the groove G is changed corresponding to other information signal in the optical disk of FIG. 2A.
Although if the width and length of the pit are changed corresponding to a modulation signal in a playback dedicated optical disk as shown in FIG. 1B, such signal characteristics as a degree of modulation and asymmetry change. However, because the signal standard has a width, there never occurs a practical problem.
Because in a recordable optical disk, its guide groove occupies most area in the recording surface of the optical disk and there are few pits already recorded, the length of the groove cannot be changed in the length direction corresponding to the modulation signal. Therefore, as shown in FIG. 2B, the width of the groove is changed corresponding to the modulation signal. However, in this case, the area of the recording region in an adjacent land changes, thereby affecting the record playback characteristic of information signal in that region badly.
In views of the above problems, an object of the present invention is to provide an optical disk capable of recording a first information signal by forming a groove in the direction of a recording track and then forming rows of marks or dots on the groove or a land, in which a second information signal can be also recorded without affecting the playback characteristic of the first information signal badly.
Another object of the present invention is to provide an optical disk in which the first information signal is recorded by forming rows of marks or dots on a flat recording surface, wherein it is capable of recording a second information signal without affecting the playback characteristic of the first information signal badly.
Still another object of the present invention is to provide a recording method for an optical disk for recording a first information by forming rows of marks or dots on a flat recording surface, in which it is capable of recording a second information signal without affecting the playback characteristic of the first information signal badly.
A further object of the present invention is to provide an optical disk in which grooves are formed in the direction of the recording track and which is capable of recording an information signal by forming rows of marks or dots on the groove or land corresponding to the information signal, wherein the optical disk is capable of expressing characters, graphic or symbol on its recording surface.
A still further object of the present invention is to provide a production apparatus for a master disk for an optical disk comprising a laser light or beam source and an objective lens for converging the laser beam emitted from the laser beam source and irradiating the same on an exposure master disk and capable of forming groove capable of recording a first information signal by irradiating the converged beam from the objective lens on the exposure master disk so as to form rows of marks or dots on the groove or land, in which the optical disk is also capable of recording a second information signal without affecting the playback characteristic of the first information signal badly.
A yet still another object of the present invention is to provide a production apparatus for a master disk of an optical disk comprising a laser light or beam source and an objective lens for converging the laser beam emitted from the laser beam source and irradiating the same on an exposure master disk and capable of recording a first information signal on the exposure master disk with rows of marks or dots by modulating the laser beam by the first information signal, in which the optical disk is capable of also recording a second information signal without affecting the playback characteristic of the first information signal badly.
To achieve the above objects, according to a first aspect of the invention, there is provided an optical disk containing grooves formed in a direction of a recording track and in which by forming rows of marks or dots corresponding to a first information signal on the groove or land, the first information signal is recorded, wherein a second information signal is recorded at least in part of the groove, wherein the second information signal is recorded by forming a wave having a spatial frequency higher than a cut-off frequency of a playback optical system corresponding to the second information signal, on a part or all of the groove.
In the optical disk of the first aspect of the present invention, by forming the wave having a spatial frequency higher than the cut-off frequency of the playback optical system corresponding to the second information signal on a part or all of the groove, the second information signal is recorded.
According to a first aspect of the present invention, there is provided an optical disk containing grooves formed in a direction of a recording track and in which by forming row of marks or dots corresponding to a first information signal on the groove or land, the first information signal is capable of being recorded, wherein a second information signal is recorded by forming a wave having a spatial frequency higher than a cut-off frequency of a playback optical system corresponding to the second information signal on a part or all of the groove.
According to a second aspect of the present invention, there is provided an optical disk in which by forming rows of marks or dots on a flat recording surface, a first information signal is recorded, wherein a second information signal is recorded by waving a part of marks or dots in the row of marks or dots or all of the marks or dots corresponding to the second information signal at a spatial frequency higher than the cut-off frequency of a playback optical system.
According to a third aspect of the present invention, there is provided a recording method for an optical disk for recording a first information signal by forming rows of marks or dots on a flat recording surface having a step for recording a second information signal by waving a part of marks or dots in the row of marks or dots or all of the marks or dots in correspondence with the second information signal at a spatial frequency higher than the cut-off frequency of a playback optical system.
According to a fourth aspect of the present invention, there is provided an optical disk according to the first aspect of the invention, wherein a wave is formed on a part of the groove and an average of the width of a part of the groove having the wave is substantially the same as an average of the width of a part of the groove without the wave.
According to a fifth aspect of the present invention, there is provided an optical disk according to the first aspect of the present invention, wherein a wave is formed in a part of the groove and the second information signal is recorded corresponding to absence or presence of the wave of the groove.
According to a sixth aspect of the present invention, there is provided an optical disk according to the first aspect of the present invention, wherein the second information signal is recorded by changing an amplitude of the wave of the groove to two or more stages.
According to a seventh aspect of the present invention, there is provided an optical disk according to the second aspect of the present invention, wherein the wave is partially formed on a part marks or dots in the row of marks or dots or all of the marks or dots and the second information signal is recorded corresponding to absence or presence of the wave of the mark or dot.
According to an eighth aspect of the present invention, there is provided an optical disk according to the second aspect of the present invention, wherein the second information signal is recorded by changing the amplitude of the wave in a part of marks or dots in the row of the marks or dots or all of the marks or dots at two or more stages.
According to a ninth aspect of the present invention, there is provided a recording method for an optical disk according to the third aspect of the present invention, wherein the wave is partially formed on a part of marks or dots in the row of marks or dots or all of the marks or dots and the second information signal is recorded corresponding to absence or presence of the wave of the mark or dot.
According to a tenth aspect of the present invention, there is provided a recording method for an optical disk according to the third aspect of the present invention, wherein the second information signal is recorded by changing the amplitude of the wave in a part of marks or dots in the row of the marks or dots or all of the marks or dots at two or more stages.
According to an eleventh aspect of the present invention, there is provided an optical disk containing grooves formed in a direction of a recording track and in which by forming rows of marks or dots corresponding to an information signal on the groove or land, the information signal capable of being recorded, wherein a wave for expressing characters, graphic or symbol is formed in a part or all of the groove.
According to a twelfth aspect of the present invention, there is provided a production apparatus for a master disk for an optical disk comprising a laser light or beam source and an objective lens for converging a laser beam emitted from the laser beam source and irradiating the same on an exposure master disk so as to form rows of marks or dots on the groove or land thereby a groove capable of recording a first information signal being formed, the production apparatus further comprising a beam deflector for wobbling the converged beam to be irradiated on the exposure master disk in a direction intersecting a track in accordance with a second information signal, wherein the second information signal is recorded by forming a wave with a spatial frequency higher than the cut-off frequency of the playback optical system on a part or all of grooves in response to the second information signal.
According to a thirteenth aspect of the present invention, there is provided a production apparatus for a master disk for an optical disk comprising a laser light or beam source and an objective lens for converging a laser beam emitted from the laser beam source and irradiating the same on an exposure master disk, in which an first information signal is recorded on the exposure master disk with a row of marks or dots by modulating the laser beam by the first information signal, the production apparatus further comprising a beam deflector for wobbling the converged beam to be irradiated on the exposure master disk in a direction intersecting a track in correspondence with a second information signal, the second information signal being recorded by waving a part of marks or dots in the row of marks or dots or all of the marks or dots corresponding to the second information signal at a spatial frequency higher than the cut-off frequency of a playback optical system.